It will dock with the Tiangong-1 space module and the crew will transfer supplies to the space lab, which has been in orbit since September 2011. During the 15-day mission, the crew will master the rendezvous and docking capabilities that are essential for the operation of a manned space platform.

"The functionality, performance, and coordination of all systems will be evaluated during this mission," Wu Ping, a spokesperson for China's Manned Space Program, told a news conference on Monday.

Photos:Photos: China launches three into space

Photos:Photos: China launches three into space

China launches three into space – China's Shenzhou 10 rocket blasts off from the Gobi Desert in the city of Jiuquan, in China's Gansu province, on Tuesday, June 11. The craft is scheduled to dock with the Tiangong-1 space module, where the three crew members will transfer supplies to the space lab, which has been in orbit since September 2011.

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Photos:Photos: China launches three into space

China launches three into space – Chinese technicians congratulate each other after the Shenzhou-10 rocket successfully launched on June 11. This is expected to be China's longest flight with astronauts on board.

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Photos:Photos: China launches three into space

China launches three into space – Chinese chief mission commander Zhang Youxia salutes after he announced the successful launch.

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Photos:Photos: China launches three into space

China launches three into space – The spaceship blasts off on June 11.

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China launches three into space – Chinese astronaut Wang Yaping, left, mission commander Nie Haisheng and Zhang Xiaoguang wave to onlookers as they prepare to board on June 11.

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China launches three into space – Yaping, Xiaoguang and Haisheng wave on June 11.

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China launches three into space – The crew attend a press conference in Jiuquan on Monday, June 10.

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China launches three into space – Yaping speaks to the media on June 10.

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China launches three into space – Haisheng trains on May 8.

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China launches three into space – Xiaoguang, left, Haisheng and Yaping sit in a simulated spaceship capsule on April 29.

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Humans in space

She added that another main objective of the mission was to test technologies related to the construction of a space station, as China seeks to establish a long-term human presence in space.

"These longer duration missions and space dockings are essential practice for any kind of long-term, more permanent presence in space or a mission to, say, the moon," said Dean Cheng, a research fellow at the Washington-based Heritage Foundation.

China's march into space underscores the country's growing financial and military clout and has unsettled some Western observers.

A 92-page report on Chinese military development released by the Pentagon last month highlighted the advances in China's space capabilities.

"China is developing a multi-dimensional program to improve its capabilities to limit or prevent the use of space-based assets by adversaries during times of crisis or conflict," the report said.

A spokeswoman for China's manned space missions said last year the program would cost a total of almost 40 billion yuan (US$6.27 billion).

The U.S. closed its space shuttle program in 2011 and is no longer aggressively pursuing manned space exploration, leaving Russia and China as the only two countries in the world capable of independently sending humans into space.

"In some ways, they have overtaken the US, at least temporarily," says the Heritage Foundation's Cheng. "Of course, the US, and even more Russia, have more experience in manned space. China is not, at this time, capable of reaching the Moon."

"But like the tortoise and the hare, China is slowly catching up with the US."

However, Cheng says that China is not engaged in a space race with the US. Rather: "They have a long-term plan, and they are sticking to it."

Private space ambitions

Companies like Boeing, Space X and Virgin Galactic are scrambling to develop private sector spacecraft and operate in what has previously been the exclusive preserve of sovereign nations.

China is not part of the project that maintains the International Space Station (ISS), which currently orbits the Earth conducting experiments in a range of fields, from physics to astronomy.

The ISS is a joint venture between NASA, Russia's RKA space agency, Japan's Aerospace Exploration Agency, the European Space Agency and the Canadian CSA.

China views its multi-billion dollar space program as a way to raise prestige both domestically and abroad. This is the first high-profile space launch since new leader Xi Jinping assumed the presidency in March.

Public reaction to the planned mission was mixed, with some users of the Twitter-like Weibo platform wishing the astronauts well, while others said the resources were best used on the ground.

"Our country may be lagging behind in other areas, but China has great achievement in aerospace technology," said one user with the handle @Jiniaobieliulin.

"The government should spend more money to help those of lowest social status," said another user identified as @Xiaoxiaojuna.